Show Me the Numbers

Using Research

The topic of the the latest AVBRN doulas meeting was all about navigating current research and implementing it into a doula practice. Since the majority of doulas and midwives are not PhD clinical researchers, the information is highly relevant but, honestly, it’s pretty boring. Doulas and the families they serve are interested mainly on the plain language summaries and not so much with the pages upon pages of double-blind research tables.

On the heels of that recent meeting of the minds, I came across this article by Plumbtree Baby discussing how care providers have been known to counsel families using subtle (or sometimes not so subtle) coercion by presenting information in terms of relative risk instead of absolute risk.

While the topic could be anything regarding making a baby, I’m going to use the highly studied and hotly debated topic of Uterine Rupture in Pregnancy, cesarean surgeries, trial of labor after cesarean (TOLAC), and vaginal birth after cesarean (VBAC) as an example.

“Women attempting a VBAC are 40 times more likely to experience a uterine rupture!”

That’s a relative risk. The explicit inference is that if you attempt to have a baby vaginally after you’ve had a cesarean then you’re putting your baby’s life at risk by a factor of 40. While that’s completely true, it’s not necessarily as scary as it sounds and it’s certainly not the whole story.

“Women attempting a VBAC have a rate of uterine rupture of 0.5% compared to women who have not had a cesarean which is 0.012%.”

While both statements are numerically accurate, I think we can all agree that the second statement doesn’t sound anywhere near as bad as the first. Also, I think it’s fair to say that the first statement doesn’t really paint the whole picture.

That’s the difference between relative risk and and absolute risk. So when you’re talking with your care provider and they make general statements about procedures, interventions, or medications in terms of “X times more likely” or “XX% increase” ask for the absolute data. Your doctor may not have those numbers memorized but should be able to provide them to you.

So you don’t have to go look it up yourself, here’s the text from the above linked article (emphasis added):

Uterine rupture is a rare but often catastrophic obstetric complication with an overall incidence of approximately 1 in 1,536 pregnancies (0.07%). In modern industrialized countries, the uterine rupture rate during pregnancy for a woman with a normal, unscarred uterus is 1 in 8,434 pregnancies (0.012%).

The vast majority of uterine ruptures occur in women who have uterine scars, most of which are the result of previous cesarean deliveries. A single cesarean scar increases the overall rupture rate to 0.5%, with the rate for women with 2 or more cesarean scars increasing to 2%

Speaking of cesarean surgeries…

Why is it that families have to shop high and low for a care provider who will support their decision for a TOLAC? When ACOG says not only are ladies who have had a previous c-section candidates for VBAC, but they should be counseled about it and offered a TOLAC, why do women have to look for a care provider who holds this view in the first place?

Consistent with past recommendations, most women with one previous cesarean
delivery with a low-transverse incision are candidates for and should be counseled
about VBAC and offered a TOLAC.